Let G$\DeclareMathOperator\rk{rk}$ Let $G$ be a finite metabelian p$p$-group, i.e. the commutator subgroup G'$G'$ of G$G$ is abelian. Then I ask myself under which conditions does the following hold:
rk(G' \cap Z(G)) \le rk(G/G') (*)
$$\tag{$*$} \rk(G' \cap Z(G)) \le \rk(G/G')$$
where Z(G)$Z(G)$ is the centre of G$G$. I have constructed examples where (*)$(*)$ does not hold, but in most cases it does hold. Do you know of any results in the literature ? How high would you guess the percentage of p$p$-groups satisfying (**)$(**)$ in a numerical analysis ?
Thanks a lot.